A more thorough explanation:

Definition: To challenge or call into question a person's character or the truth of a statement.

Example 1: The lawyer tried to impugn the witness's credibility by bringing up her past criminal record.

Example 2: The journalist impugned the politician's claim by presenting evidence that contradicted it.

Explanation: When someone impugns another person or statement, they are essentially saying that they don't believe it or that it's not trustworthy. In example 1, the lawyer is trying to make the witness seem untrustworthy by bringing up her past criminal record. In example 2, the journalist is questioning the politician's claim by presenting evidence that contradicts it. Both examples illustrate the act of impugning someone or something.